Project 5 — The Quiz Application

// quiz.cpp — Programming Fundamentals Using C++
// Project 5 · The Quiz Application
// Build: g++ -std=c++17 -Wall -Wextra quiz.cpp -o quiz

#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
using namespace std;

// The bank: 8 MCQs on Units 01-06. Adding a question = adding to these vectors.
// Parallel-vector scaffolding — Unit 14's struct will replace it cleanly.

void loadBank(vector<string>& q, vector<string>& o1, vector<string>& o2,
              vector<string>& o3, vector<string>& o4, vector<int>& answer,
              vector<string>& why) {
    q.push_back("What does a compiler do?");
    o1.push_back("Runs the program line by line");
    o2.push_back("Translates source code to machine code");
    o3.push_back("Formats the source code");
    o4.push_back("Stores variables");
    answer.push_back(2);
    why.push_back("A compiler translates the whole source to machine code before running.");

    q.push_back("Which type holds 3.14 exactly-ish?");
    o1.push_back("int"); o2.push_back("char"); o3.push_back("double"); o4.push_back("bool");
    answer.push_back(3);
    why.push_back("double is the floating-point type for fractional values.");

    q.push_back("What does cin >> x leave in the buffer?");
    o1.push_back("Nothing"); o2.push_back("The newline"); o3.push_back("The value"); o4.push_back("An error");
    answer.push_back(2);
    why.push_back(">> leaves the newline, which is why getline needs cin.ignore after it.");

    q.push_back("Which loop runs at least once?");
    o1.push_back("while"); o2.push_back("for"); o3.push_back("do-while"); o4.push_back("none");
    answer.push_back(3);
    why.push_back("do-while tests the condition after the body.");

    q.push_back("What prints: cout << 7 / 2;");
    o1.push_back("3.5"); o2.push_back("3"); o3.push_back("4"); o4.push_back("error");
    answer.push_back(2);
    why.push_back("Integer division truncates: 7/2 is 3.");

    q.push_back("Which operator is the equality test?");
    o1.push_back("="); o2.push_back("=="); o3.push_back("==="); o4.push_back("!=");
    answer.push_back(2);
    why.push_back("== compares; = assigns.");

    q.push_back("A sentinel is...");
    o1.push_back("A loop counter");
    o2.push_back("A special value ending input");
    o3.push_back("A kind of if");
    o4.push_back("The loop body");
    answer.push_back(2);
    why.push_back("A sentinel is the agreed value that means 'no more data'.");

    q.push_back("How many times does for(int i=0;i<3;++i) run?");
    o1.push_back("2"); o2.push_back("3"); o3.push_back("4"); o4.push_back("forever");
    answer.push_back(2);
    why.push_back("i = 0, 1, 2 — three iterations.");
}

bool askQuestion(const vector<string>& q, const vector<string>& o1, const vector<string>& o2,
                 const vector<string>& o3, const vector<string>& o4, const vector<int>& answer,
                 const vector<string>& why, size_t index, char& given) {
    cout << "\n" << q[index] << "\n";
    cout << "  1. " << o1[index] << "\n"
         << "  2. " << o2[index] << "\n"
         << "  3. " << o3[index] << "\n"
         << "  4. " << o4[index] << "\n";

    int choice;
    cout << "Your answer (1-4): ";
    cin >> choice;
    while (choice < 1 || choice > 4) {          // invalid: re-prompt, never score
        cout << "Answer with 1-4: ";
        cin >> choice;
    }
    given = static_cast<char>('0' + choice);

    bool correct = (choice == answer[index]);
    cout << (correct ? "Correct! " : "Wrong. ") << why[index] << "\n";
    return correct;
}

void runSession(const vector<string>& q, const vector<string>& o1, const vector<string>& o2,
                const vector<string>& o3, const vector<string>& o4, const vector<int>& answer,
                const vector<string>& why, size_t length,
                vector<size_t>& askedIndexes, vector<char>& givenAnswers) {
    int correct = 0;
    askedIndexes.clear();
    givenAnswers.clear();

    for (size_t i = 0; i < length; ++i) {
        char given;
        if (askQuestion(q, o1, o2, o3, o4, answer, why, i, given)) ++correct;
        askedIndexes.push_back(i);
        givenAnswers.push_back(given);
    }

    int percent = static_cast<int>(correct * 100 / length);
    cout << "\nScore: " << correct << "/" << length << " (" << percent << "%)\n";
    if      (percent >= 80) cout << "Excellent\n";
    else if (percent >= 60) cout << "Good\n";
    else if (percent >= 40) cout << "Keep practising\n";
    else                    cout << "See the tutor\n";

    if (correct == length) {
        cout << "Perfect session — nothing to review\n";
    } else {
        cout << "\nReview of wrong answers:\n";
        for (size_t i = 0; i < askedIndexes.size(); ++i) {
            size_t qi = askedIndexes[i];
            if (givenAnswers[i] - '0' != answer[qi])
                cout << "  " << q[qi] << "\n    you said " << givenAnswers[i]
                     << " — " << why[qi] << "\n";
        }
    }
}

int main() {
    vector<string> q, o1, o2, o3, o4, why;
    vector<int> answer;
    loadBank(q, o1, o2, o3, o4, answer, why);

    int sessions = 0, bestPercent = -1;

    int choice;
    do {
        cout << "\n=== QUIZ ===\n1 Quick (3) · 2 Standard (5) · 3 Full bank ("
             << q.size() << ") · 4 Stats · 0 Quit: ";
        cin >> choice;

        if (choice >= 1 && choice <= 3) {
            size_t length = (choice == 1) ? 3 : (choice == 2) ? 5 : q.size();
            vector<size_t> asked;
            vector<char> given;
            runSession(q, o1, o2, o3, o4, answer, why, length, asked, given);

            ++sessions;
            int correct = 0;
            for (size_t i = 0; i < asked.size(); ++i)
                if (given[i] - '0' == answer[asked[i]]) ++correct;
            int percent = static_cast<int>(correct * 100 / asked.size());
            if (percent > bestPercent) bestPercent = percent;
        } else if (choice == 4) {
            cout << "Sessions played: " << sessions << "\n";
            if (bestPercent >= 0) cout << "Best score: " << bestPercent << "%\n";
        } else if (choice != 0) {
            cout << "Invalid choice\n";
        }
    } while (choice != 0);

    cout << "Goodbye — " << sessions << " session(s) this run\n";
    return 0;
}